1. Field of the Invention
The present invention relates to a sliding mode control method capable of preventing vibration of a machine which tends to occur by an action of a spring element of the machine when the operating condition of the machine changes.
2. Background of the Related Art
It is known to effect the feedforward compensating operation of correcting in advance the control output by considering variation in various factors, caused by variation in the machine operating condition and acting as disturbance for the control operation, so as to prevent deterioration in the controllability of a control system which would be otherwise caused when the machine operating condition has largely varied. For example, in a control system for use with a machine which includes a speed reducer disposed between a driving source and a machine operating section and acting as a spring element and a damper element, the viscous friction coefficient and spring coefficient of the speed reducer which nonlinearly vary with variation in the position and speed of the mechanical operating section are determined, and the feedforward compensating operation for acceleration is effected on the basis of the thus determined coefficients. However, according to the conventional method mentioned above, the control performance of the control system is lowered and hence vibration occurs in the machine operating section, if the viscous friction coefficient and spring coefficient cannot be precisely determined. Namely, it is difficult to provide a robust control system.